The present invention generally relates to apparatus and methods for treatment of air streams in an environmental control system to remove water vapor, and more particularly, to apparatus and methods of improving the operation of a subsystem of the environmental control system made of an air turbine and a water removal device downstream from the turbine.
In the aerospace industry, aircraft typically have sophisticated environmental control systems where humid air is often transported into the system and is cooled. When the humid air is cooled, water vapor from the air condenses and water droplets are formed. The entrained water must be removed from the air stream in order to protect rotating machinery and electronics. Excessive water can also create passenger and pilot discomfort. Removing as much water as possible from the air also benefits the hardware, electronics, crew as well as the performance of the system.
In some systems, the water is condensed when the air stream is cooled in the air turbine. The problem is that the droplets of water created and discharged by the air turbine are usually difficult to remove with conventional methods because the droplets are extremely small. Typically, an inertial water separator downstream of the turbine takes the water droplets and applies centrifugal forces to separate the water from the air stream. The typical water separator would be a large housing containing a built-in coalescer bag made of cloth inside the housing. The coalescer bag converts small droplets into larger droplets and the water separator device swirls the air to cause the water droplets to separate from the air stream.
One problem is that the coalescer bag, although efficient under optimal conditions, is sensitive to dirt, which means that if the air contains particles of dirt, which it often does, the coalescer bag cannot function properly. A further problem with this subsystem is that the coalescer bag is also sensitive to icing, which means that if the water in the air freezes, the coalescer bag also cannot function properly. Since these are relatively frequent conditions, a water separator containing a coalescer bag is not an ideal way to remove water. Yet another problem with the coalescer bag is that it requires frequent maintenance, which can be costly.
As can be seen, there is a need for an improved apparatus and method that can efficiently remove water from the air stream in these systems which does not have the undesirable sensitivities of the prior art and which has low maintenance requirements. Furthermore, there is a need to accomplish this with a simple apparatus and method that is efficient and cost-effective.